Most modern weapon systems such as tanks and attack helicopters have thermal sights. Through its ability to sense infrared energy emissions, this sight allows the gunner to acquire, identify, and engage targets in darkness, smoke, fog and rain. Each potential target (vehicle) has a distinct infrared signature relative to heat emitting areas of the body and mode of operation, i.e. running or at idle. This sophisticated equipment has produced a need for a thermalized target which simulates the thermal signature as well as a visual silhouette. In other words the days of the simple "X" painted on a piece of plywood are over.
One of the early thermal targets proposed for military use is represented by U.S. Pat. No. 4,253,670.
However, most successful target systems employed today use electric heating elements referred to as thermal blankets. Typically, these units consist of a conductive coating on a sheet of plastic or paper with two thin copper buss bars attached parallel to each other along the edges of the coated area. The electrical resistance of the coating between the buss bars create heat as a current potential is induced across it.
The heating elements are placed is an array on a plywood silhouette, usually the front or flank view, to simulate a thermal image or signature. Wires are attached to the buss bars and run along the edge of the target to an electric power source at the bottom. Typically, the target is mounted on a lifting mechanism behind an earth berm or bunker. It is raised as required during the training scenario for the gunners to engage.
The blanket system has many deficiencies which impose delays in training. The major shortcoming is the vulnerability of the wire leads and buss bars to open circuits caused by a projectile severing the same during a shooting exercise. The open circuit stops the flow of electricity to the resistance element which causes failure to provide the thermal image. To reactivate the target, it is necessary to stop the exercise and replace or repair broken buss bars and wiring. This is time consuming and costly, particularly considering the manpower and equipment involved.
To eliminate the susceptibility to open circuits as projectiles pass through the targets, the heating elements' buss bars and wiring must be made totally redundant. This can be accomplished to a limited degree with double power feeds, one from each end, to the heating elements. However, there is still a chance that the redundant buss bars could be severed given their location and vulnerability of their location relative to the thermal image. Even with redundant wiring, a buss bar could receive multiple hits along its length which would render the area between the breaks inoperative and require repair.